The present invention relates to disc drive systems for storing information. More specifically, the present invention relates to a hydrodynamic bearing assembly which provides support and rotation for a high speed spindle element.
The predominant trend in the disc drive industry for the past several years has been to increase track density in order to achieve increased data storage capacity. One of the difficulties which must be overcome in achieving this goal is the ability to maintain tracking position accuracy as the track density increases.
A major source of tracking position inaccuracy in a computer disc drive system is spindle bearing motion which is commonly referred to as "runout". Conventional spindle bearings include ball bearing assemblies which are prone to numerous mechanical problems, such as large runout, substantial wear, capacious manufacturing requirements, and the like.
A hydrodynamic bearing is an alternative to conventional ball bearing spindle systems. In a hydrodynamic bearing assembly, a lubricating fluid functions as the actual bearing surface between a stationary base and the rotating spindle or hub. The lubricating fluid typically includes either air or liquid. The rotating hub causes the fluid to circulate through the hydrodynamic bearing. When the hub is stationary, the fluid is at rest.
Hydrodynamic bearing assemblies suffer from a number of disadvantages. For example, the hydrodynamic fluid must be sealed within the spindle so that it does not escape into the disc environment. Further, tolerance between components can be very small, particularly for disc density drives. The components are relatively delicate and can be damaged during assembly.